In 2012/13, according to the U.S. Department of Agriculture (USDA), total corn production amounted 10.78 billion bushels of which 4.64 billion bushels was used for ethanol and its by-products.
These by-products include wet and dry distillers grains, CO2 and corn oil.
Distillers grains are co-products of the dry mill ethanol process and used as animal feed. According to the U.S. Grains Council, most ethanol plants are dry-grind facilities that extract starch from corn to produce ethanol. The graphic above from the Renewable Fuels Association (RFA) provides a clear view of the ethanol production process.
The remainder of the corn kernel is used to produce wet distiller grains (WDG) or dried distillers grains (DDG), of which the latter has a longer shelf life, which is then supplied to livestock and poultry producers.
DDGs contain high energy, mid-protein and high digestible phosphorus content which makes it an attractive replacement for traditionally expensive animal feed made from corn or soybean.
According to the Minnesota Department of Agriculture, the state is the third largest producer of DDGs in the country with 2.95 million metric tons produced in 2011. In fact DDGs comprised 30% of total animal feed in Minnesota that year.
"ONE TON OF DDGS IS EQUAL TO 1.22 TONS OF CORN AND SOYBEAN MEAL."Source : USDA
Furthermore, the USDA states that one ton of DDGs could effectively replace 1.22 tons of feed consisting of corn and soybean meal. In 2015, according to a study by ABF Economics, the ethanol industry produced 3.6 million tons of DDGs. The amount produced, the study said, was sufficient to meet the annual feed requirements of the entire inventory of cattle and calves in Minnesota or more than 2.7 million beef and dairy cattle.
Another co-product from the ethanol production process is CO2, which is used to carbonate beverages and make dry ice. More recently, corn oil has also been produced from ethanol production, which in turn is used in the biodiesel production process. Several ethanol producers in Minnesota such as Highwater Ethanol, Al-Corn Clean Fuel, Guardian Energy and Green Plains Renewable produce corn oil.
In 2015, Minnesota's ethanol industry produced 198 million pounds of corn oil. The study by ABF Economics said the corn oil produced by Minnesota's ethanol industry could produce over 26 million gallons of biodiesel or more than 40 percent of the biodiesel produced by Minnesota's biodiesel plants.